Compensation techniques for substrate heating processes

ABSTRACT

Methods for compensating for a thermal profile in a substrate heating process are provided herein. In some embodiments, a method of processing a substrate includes determining an initial thermal profile of a substrate that would result from subjecting the substrate to a process; determining a compensatory thermal profile based upon the initial thermal profile and a desired thermal profile; imposing the compensatory thermal profile on the substrate prior to performing the process on the substrate; and performing the process to create the desired thermal profile on the substrate. The initial substrate thermal profile can also be compensated for by adjusting a local mass heated per unit area, a local heat capacity per unit area, or an absorptivity or reflectivity of a component proximate the substrate prior to performing the process. Heat provided by an edge ring to the substrate may be controlled prior to or during the substrate heating process.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/561,851, filed Nov. 20, 2006, by Ranish, et al., and entitled“Compensation Techniques For Substrate Heating Processes,” whichapplication is incorporated by reference herein.

BACKGROUND

1. Field

Embodiments of the present invention generally relate to substrateprocessing techniques. More specifically, the present invention relatesto processing techniques for creating desired thermal profiles duringsubstrate processing.

2. Description of the Related Art

Rapid thermal processing (RTP) and rapid thermal chemical vapordeposition (RTCVD) annealing processes, and the like (collectively andgenerically referred to herein as “conventional heating processes”),traditionally use a furnace with infrared radiation generated by halogenlamps to heat a substrate. The substrate, commonly made of silicon, isdisposed in a controlled atmosphere enclosure, and the infraredradiation is directed onto the superficial face of the substrate througha transparent window.

The temperatures reached during thermal processing operations may behigh, often over 1000° C., with thermal gradients liable to reachseveral 100° C./second or higher. One important parameter of suchsubstrate processing is the uniformity of the temperature over theentire surface of the processed substrate. The presence of thermalgradients of just a few degrees between the various portions of thesubstrate can cause defects in the substrate. However, heat loss nearthe edges of the substrate is much greater than near the center, whichleads to lower temperatures at the edge of the substrate.

Several solutions have been proposed to compensate for this temperatureinequality. Some examples include: a metal reflector positioned at therear of the lamps, heating both sides of the substrate with two sets oflamps arranged along opposite sides of the reactor, heating by zones inthe reactor, the use of heated susceptors, and fitting an edge ring tominimize heat transfer through the sides of the substrate. However,despite any improvements these solutions may have provided, thermalgradients continue to exist sufficient to cause defects in thesubstrates.

Therefore, there is a need in the art for a method and apparatus thatgenerates desired substrate thermal profiles when subjected to theseheating processes.

SUMMARY

Methods for compensating for a thermal profile in a substrate heatingprocess are provided herein. In one embodiment, a method of processing asubstrate includes determining an initial thermal profile of a substrateresulting from a process; imposing a compensatory thermal profile on thesubstrate based on the initial thermal profile; and performing theprocess to create a desired thermal profile on the substrate.

In another embodiment, a method of processing a substrate includesdetermining an initial thermal profile of a substrate resulting from aprocess; adjusting a local amount of mass heated per unit area of acomponent proximate the substrate in response to the initial thermalprofile; and performing the process to create a desired thermal profileon the substrate.

In another embodiment, a method of processing a substrate includesdetermining an initial thermal profile of a substrate resulting from aprocess; adjusting a local heat capacity per unit area of a componentproximate the substrate in response to the initial thermal profile; andperforming the process to create a desired thermal profile on thesubstrate.

In another embodiment, a method of processing a substrate includesdetermining an initial thermal profile of a substrate resulting from aprocess; controlling the heat provided by an edge ring to the substratein response to the initial thermal profile; and performing the processto create a desired thermal profile on the substrate.

In another embodiment, a method of processing a substrate includesdetermining an initial thermal profile of a substrate resulting from aprocess; adjusting an absorptivity or a reflectivity of a componentproximate the substrate in response to the initial thermal profile; andperforming the process to create a desired thermal profile on thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings.

FIG. 1 depicts a schematic, cross-sectional view of a substrate processchamber in accordance with one embodiment of the present invention;

FIG. 2 depicts an illustration of an initial thermal profile of thesubstrate of FIG. 1;

FIG. 3 depicts a graphical representation of the initial thermal profileof the substrate of FIG. 1, along axis 3-3 of FIG. 2;

FIG. 4 depicts a graphical representation of a compensatory thermalprofile used to compensate for the initial thermal profile of FIGS. 2and 3 in accordance with one embodiment of the invention;

FIG. 5 depicts a flowchart of one embodiment of a method for creating adesired thermal profile for a substrate;

FIG. 6 depicts a flowchart of one embodiment of a method for creating adesired thermal profile for a substrate;

FIG. 7 depicts a schematic, cross-sectional view of a susceptor inaccordance with one embodiment of the present invention;

FIG. 8 depicts a schematic, cross-sectional view of a susceptor inaccordance with one embodiment of the present invention; and

FIG. 9 depicts a flowchart of one embodiment of a method for creating adesired thermal profile for a substrate.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments. Where possible, identical referencenumerals are used herein to designate identical elements that are commonto the figures.

DETAILED DESCRIPTION

The present invention provides methods for processing a substrateutilizing thermal compensation techniques either prior to or during aheating process for creating a desired thermal profile for a substrateduring processing.

FIG. 1 is a schematic cross-sectional view of a process chamber 100 inaccordance with one embodiment of the present invention. The processchamber 100 is suitable for thermally processing substrates 130 such assemiconductor wafers, glass or sapphire substrates, and the like. Asused herein, thermally processing refers to any process performed on asubstrate in which the temperature of the substrate is controlled.Accordingly, the process chamber 100 may be adapted for performing atleast one of deposition processes, etch processes, plasma-enhanceddeposition and/or etch processes, and thermal processes, among otherprocesses performed in the manufacture of integrated semiconductordevices and circuits. Specifically, such processes may include, but arenot limited to, rapid thermal processes (RTP), rapid thermal chemicalvapor deposition (RTCVD), annealing processes (such as flash annealing),and the like.

In the embodiment depicted in FIG. 1, the process chamber 100illustratively comprises a chamber body 102, support systems 160, and acontroller 150. The chamber body 102 generally includes an enclosure 104having an upper portion 106, a lower portion 108, and, optionally, achamber divider 170.

Typically, one or more heat sources 110, a susceptor 120, and asusceptor lift 122 may be disposed within the chamber body 102. Thesusceptor 120 is configured to support a substrate 130 thereupon.Optionally, an edge ring 140 may be disposed upon the susceptor 120. Theedge ring 140 is generally configured to surround the substrate 130 andmay optionally include a heating element, such as a resistive heater142. Optionally, the substrate 130 may be held by the edge ring 140 andthe susceptor 120 may be absent.

The heat sources 110 may be disposed at any location throughout thechamber. Typically, the heat sources 110 are disposed in at least oneportion of the chamber, for example, the upper portion 106 and/or thelower portion 108 of the chamber body 102, and may be separated by thechamber divider 170. However, some embodiments may provide heat sources110 on a side 180 of the chamber in addition to or instead of in theupper portion 106 and/or the lower portion 108. Suitable heat sources110 include heat lamps, hot plates, bottom-radiant devices, infrared(IR) radiation sources, or any other type of heat source suitable forheating the substrate 130.

The susceptor 120, which serves as a support surface for the substrate130, is disposed on a susceptor lift 122 in the lower portion 108 of theprocess chamber 100. The susceptor lift 122 may readily raise and lowerthe susceptor 120 and substrate 130 as desired. The substrate 130 isplaced on the susceptor 120 and during a heating process, a temperaturedistribution is formed across the surface of the substrate 130 by theheat sources 110 (which may vary from a center 131 to an edge 132 of thesubstrate 130). Depending on the type of process being performed, anedge ring 140 may optionally be used to modify the thermal behavior ofthe edge (for example, by supplying or removing heat to the substrateedge for higher/lower heating rates, such as by conductivelyproviding/removing heat to or from the substrate edge and/or byreflecting radiation onto the substrate edge or shielding the substrateedge from radiation, or the like).

The support systems 160 of the process chamber 100 include componentsused to execute and monitor pre-determined processes (e.g., growingepitaxial silicon films) in the process chamber 100. Such componentsgenerally include various sub-systems (e.g., gas panel(s), gasdistribution conduits, vacuum and exhaust sub-systems, and the like) anddevices (e.g., power supplies, process control instruments, and thelike) of the process chamber 100. These components are well known tothose skilled in the art and are omitted from the drawings for clarity.

The controller 150 generally comprises a central processing unit (CPU)152, a memory 154, and support circuits 156 and is coupled to andcontrols the process chamber 100 and support systems 160, directly (asshown in FIG. 1) or, alternatively, via computers associated with theprocess chamber 100 and/or the support systems 160. In one embodiment, asoftware routine 162 is disposed in the memory 154, which, whenexecuted, implements compensation techniques for an initial thermalprofile 158, discussed below.

FIGS. 2 and 3 depict illustrative top and side views, respectively, ofan initial thermal profile 158 of a substrate 130. The initial thermalprofile 158 typically corresponds to a thermal profile of the substrate130 immediately or shortly after being subjected to a heating process ina process chamber 100. The thermal profile may be determined bymeasuring a process result as a function of position on the substrate130 and converting the process result into temperature differences fromknowledge of the process activation energy. The process does notnecessarily have to be the same process as the one actually being usedin production but can be any well characterized process. For example, asilicon substrate 130 can be subjected to an atmosphere of pure oxygenduring a thermal exposure. Afterwards, the silicon dioxide thickness canbe used to infer the spatial temperature variation which will besubstantially the activation energy weighted temperature distributionduring the process. By choosing a characterization process with a verysimilar activation energy to the production process, the weightings willbe approximately the same. Alternately, the weighting can be correctedwith knowledge of the respective activation energies.

In one example, the initial thermal profile 158 may generally decreasein temperature concentrically from the center of the substrate 130 dueto more rapid heat loss near the edges of the substrate. Accordingly, inthe embodiment depicted in FIG. 2, the substrate is hottest near thecenter 131 and has a declining temperature approaching the edge 132.Although FIGS. 2 and 3 depict an initial thermal profile 158 wherein thecenter is hotter than the edges, it is contemplated that some processesmay result in different thermal profiles, including those with coolercenter portions of the substrate 130.

FIG. 4 depicts a graphical representation of a compensatory thermalprofile 159 designed to compensate for the initial thermal profile 158of FIG. 3, in accordance with one embodiment of the present invention.The compensatory thermal profile 159 is a thermal profile that, whenadded to the initial thermal profile 158, yields a desired thermalprofile 157 for the substrate 130. For example, where a desired thermalprofile 157 is a uniform thermal profile (i.e., a substantially flatprofile), the compensatory thermal profile 159 is the mathematicalinverse of the initial thermal profile 158. Thus, if the two profileswere superimposed upon one another, a graphical representation wouldappear as a straight line (e.g., thermal profile 157 in FIG. 4). So longas an initial thermal profile 158 and a desired thermal profile 157 areknown, or can be determined, a compensatory thermal profile 159 can befound by subtracting the initial thermal profile 158 from the desiredthermal profile 157. Consequently, the compensatory thermal profile 159is sought to be imposed on a substrate 130 according to embodiments ofthe present invention, as discussed in more detail below.

FIG. 5 depicts a flowchart of one embodiment of a method 500 forutilizing compensation techniques for creating a desired thermal profile157 on a substrate 130 during a heating process. The method 500 isdescribed with reference to FIGS. 1 through 4. The method 500 starts atstep 502, where the initial thermal profile 158 of the substrate causedby a heating process is determined. Different methods may be used todetermine the initial thermal profile 158 of the substrate 130,including without limitation empirical or experimental testing,computer-based modeling, mathematical modeling, and the like. Duringempirical or experimental testing, thermal profilers (such asthermocouples, optical pyrometers, radiation pyrometers or the like) maybe used to determine the initial thermal profile 158.

At step 504, the initial thermal profile 158 obtained in step 502 iscompensated for by imposing a compensatory thermal profile 159 on thesubstrate 130. In one embodiment, imposing a compensatory thermalprofile 159 involves pre-heating the substrate 130 in accordance withthe compensatory thermal profile 159. For example, if the desiredthermal profile 157 is uniform, areas of the substrate 130 which wouldnormally maintain lower temperatures after a conventional heatingprocess are pre-heated to a temperature greater than areas whichnormally maintain higher temperatures. The imposition of a compensatorythermal profile 159 may also involve shielding, or protecting particularareas of the substrate from undesired heat transfer. This embodimentprovides for the ability to achieve a desired thermal profile 157without adjusting the heating process for each substrate 130 processed.The substrate 130 may be pre-heated in the process chamber 100 or priorto being introduced into the process chamber 100.

At step 506, the substrate heating process is performed. By havingimplemented the compensatory thermal profile 159 at step 504, heatingthe substrate 130 no longer yields the initial thermal profile 158, butrather the desired thermal profile 157. For example, during a flashannealing process with a particular support/substrate geometry, it maybe determined that an initial thermal profile 158 may be hotter near thecenter of the substrate 130 and cooler near the edge of the substrate130. Accordingly, in embodiments where a substantially uniform thermalprofile is desired, the substrate 130 may be pre-heated to impose acompensatory thermal profile 159 on the substrate that corresponds tothe inverse of the initial thermal profile 158. As such, when the flashannealing process is performed on the substrate, a substantially uniformthermal profile results, instead of the non-uniform, initial thermalprofile 158. Although one thermal profile is illustratively describedabove, it is contemplated that any thermal profile may be compensatedfor using the techniques described herein.

In one embodiment, step 506 may be performed immediately after imposingthe compensatory thermal profile 159 on the substrate 130 in step 504.Alternatively, step 506 may be performed after a period of time elapses.Optionally, the compensatory thermal profile may further compensate forcooling of the substrate during any period of time between theimposition of the compensatory thermal profile and the performance ofthe thermal process. For example, if the compensatory thermal profile isimposed in a chamber remote from the processing chamber where thethermal process occurs, the compensatory thermal profile may compensatefor the cooling that occurs during the time to transport the substrateto the process chamber where the thermal process is to be performed.

FIG. 6 depicts a flowchart of another embodiment of a method 600 forutilizing compensation techniques for creating a desired thermal profilefor a substrate 130. The method 600 is described with reference to FIGS.1 through 4. The method 600 begins at step 602 where the initial thermalprofile 158 of the substrate due to a process is determined. This stepis similar to step 502 described above with respect to FIG. 5.

Next, at step 604, a local substrate heating rate adjusted to compensatefor the initial thermal profile and result in a desired thermal profile.The local substrate heating rate may be adjusted in a number of ways. Inone embodiment, useful for processes which have not reached steadystate, the amount of mass heated per unit area may be adjusted, orlocally controlled. For example, in the embodiment depicted in FIG. 7,the thickness of a susceptor 702 is varied to emulate the compensatorythermal profile 159, resulting in a change of mass at particular areasof the susceptor 702 (i.e., creating a susceptor having a compensatoryheat transfer profile). By varying the thickness of the susceptor 120,thermal properties such as heat flux, heat transfer rates, and the like,which are dependant upon the mass of the susceptor at a particularlocation, may be controlled. For example, if the susceptor 702 isthicker at a particular location, the heat transfer through thatlocation is decreased by virtue of having more mass to heat, andconversely, if the susceptor 702 is thinner at a particular location,the heat transfer through that location is increased. In theillustrative embodiment depicted in FIG. 7, the susceptor 702 has athinner section 710 disposed proximate the periphery of a substrate 130,and thicker section 720 proximate the center of the substrate 130 tocompensate for an initial heat profile determined to have a hottercenter and a cooler edge. It is contemplated that other thicknessprofiles of susceptors resulting in varying profiles of mass heated perunit area may be utilized to compensate for particular initial thermalprofiles determined for particular substrates undergoing particularthermal processes. Alternatively or in combination, the local massheated per unit area may be controlled via control of the thermalconductivity in desired locations of the susceptor. For example,different regions of the susceptor may have different thermalconductivity to emulate regions of differing mass, as discussed above.Although described as being useful for processes which have not reachedsteady state, the above techniques may have effects that persist intothe steady state regions of a process.

Alternatively or in combination, the local heat capacity per unit perunit area may be adjusted, or locally controlled. For example, in theembodiment depicted in FIG. 8, a multi-material susceptor 802 isutilized, in which material variations in the susceptor 802 change thelocal heat capacity per unit area to emulate the compensatory thermalprofile 159, resulting in a susceptor 802 having a compensatory heattransfer profile. By varying the material selection of the susceptor802, the local substrate heating rate may be controlled. The materialselection may be based on the heat transfer rate of the material. Forexample, materials with high heat capacity have lower heat transferrates. Conversely, materials having low heat capacity have higher heattransfer rates. In embodiments where an edge ring is utilized (asdepicted in FIG. 1), the material of the edge ring may similarly beselected to have a desired heat rate to compensate for the initialthermal profile of the substrate. In the illustrative embodimentdepicted in FIG. 8, the susceptor 802 may comprise a first material 810with deposits of a second material 820 and a third material 830 wherechanges in the local heat capacity per unit area are desired to controlthe local heating rates of the substrate 130 in those areas as a resultof a particular thermal process. The heat transfer rates of the first,second, and third materials may be selected to control the local heatcapacity per unit area as desired to compensate for the initial thermalprofile and result in a desired thermal profile. It is contemplated thatthe location, geometry, numbers of regions, and/or selection ofmaterials may be varied as desired for particular heating applications.

Alternatively or in combination, the absorptivity or reflectivity of anedge ring or susceptor edge may be adjusted to compensate for theinitial thermal profile 158. For example, as discussed above withrespect to FIG. 1, the material composition, surface properties (i.e.,finish, angle, or the like), or thickness of the edge ring 140 orsusceptor edge 124, may be adjusted to control the level of absorptivityor reflectivity as desired. Optical coatings or films, includingdielectric film stacks, can also be used to alter the surfaceproperties. As the local absorptivity is increased, more irradiation isretained by the edge ring 140 or susceptor edge 124, and the temperatureincreases at the substrate edge 132. Conversely, increasing the localreflectivity causes more irradiation to reflect from the edge ring 140or susceptor edge 124, resulting in a temperature decrease at thesubstrate edge 132. In another embodiment, an edge ring 140 may beprovided with an optional feature (not shown) to reflect additionalenergy to the substrate edge 132 to heat the substrate edge 132.

Returning to FIG. 6, at step 606, the thermal process is performedresulting in a desired thermal profile formed on the substrate. Thus, byinstituting one or more of the above techniques (i.e., varying the massheated per unit area, varying the heat capacity per unit area, orcontrolling the absorptivity or reflectivity of the edge ring orsusceptor edge), the heating rate of the substrate may be locallycontrolled, and thereby compensate for an initial thermal profile toyield a desired thermal profile. The effectiveness of the adjustments ofmass heated per unit area generally decreases as the heat rate increases(i.e., as the heat rate increases, the amount of mass heated-per-unitarea becomes less of a factor in determining the resulting thermalprofile of a substrate). For Example, at exceedingly high heating rateslike laser surface heating, where the irradiance on the heated piece ison the order of 1×10⁹ W/m², only the layers exposed to the radiation(those nearest the surface for visible radiation on bare silicon) areeffectively heated. Layers of substrate a couple hundred microns belowthe surface remain at the starting temperature. In this case, thethermal properties of the substrate support (mass, heat capacity, andthe like) are immaterial. The heated thickness depends on the balance ofradiation applied and heat dissipated conductively in the substrate.Therefore, although the method described above with respect to FIG. 6may be utilized in any thermal process, it is particularly useful forlow-heat processes (i.e., processes with heat rates on the order ofhundreds of degrees Celsius per second).

FIG. 9 depicts a flowchart of yet another embodiment of a method 900 forutilizing compensation techniques for creating a uniform thermal profileon a substrate. The method 900 is discussed with reference to FIG. 1.The method 900 begins at step 902 where an initial thermal profile of asubstrate due to a process is determined, similar to steps 502 and 602,discussed above with respect to FIGS. 5 and 6, respectively.

Next, at step 904, a heater disposed within the edge ring 140 (such asresistive heater 142) is controlled to heat the substrate in a mannerthat compensates for the initial thermal profile of the substrate andyields a desired thermal profile. The heater may be controlled manuallyor via the controller 150.

The average temperature of the edge ring 140 may be inferred bymonitoring the electrical resistance of the resistive heater 142. Assuch, the current supplied to the heater 142 may be controlled toproduce a temperature of the edge ring 142 that compensates for theinitial thermal profile. For example, in embodiments where the initialthermal profile of the substrate has a cooler edge (such as depicted inFIGS. 2 and 3) the temperature of the edge ring 140 may be increased toreduce the more rapid heat loss near the edge of the substrate andprovide the desired thermal profile. In other embodiments, thetemperature of the heater 142 may be kept at a lower temperature toprevent excessive heating of the edge of the substrate. Moreover, inembodiments where the edge ring has a negative temperature coefficient,the resistive heating will tend to heat the cooler regions of the edgering more and even out any non-uniformities in the edge ringtemperature.

At step 906, which may be performed subsequent to or simultaneously withstep 904, the process is performed, resulting in a substrate with asubstantially desired thermal profile.

Thus, embodiments of methods for processing a substrate utilizingthermal compensation techniques for creating a desired thermal profileon a substrate have been provided. The disclosed techniquesadvantageously compensate for non-desired initial thermal profilescaused by a process and provide for the creation of a desired thermalprofile on a substrate.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of processing a substrate, comprising: determining aninitial thermal profile of a substrate that would result from subjectingthe substrate to a process; determining a compensatory thermal profilebased upon the initial thermal profile and a desired thermal profile;imposing the compensatory thermal profile on the substrate prior toperforming the process on the substrate; and performing the process tocreate the desired thermal profile on the substrate.
 2. The method ofclaim 1, wherein the step of imposing a compensatory thermal profile onthe substrate comprises: pre-heating the substrate to establish thecompensatory thermal profile.
 3. The method of claim 2, wherein thecompensatory thermal profile is the inverse of the initial thermalprofile.
 4. The method of claim 2, wherein the pre-heating step isperformed outside of a chamber where the process is to be performed. 5.The method of claim 2, wherein the pre-heating step is performed in thesame chamber where the process is to be performed.
 6. The method ofclaim 1, wherein the process comprises one of a rapid thermal process, arapid thermal chemical vapor deposition process, or an annealingprocess.
 7. The method of claim 1, wherein the process comprises a flashannealing process.
 8. The method of claim 1, wherein the desired thermalprofile is substantially uniform.
 9. The method of claim 1, whereinimposing the compensatory thermal profile on the substrate comprises:controlling the heat provided to the substrate by an edge ring topre-heat the substrate.
 10. The method of claim 9, wherein the edge ringcomprises a resistive heater.
 11. The method of claim 10, furthercomprising: controlling the heat provided by the edge ring to thesubstrate while performing the process.
 12. A method of processing asubstrate, comprising: determining an initial thermal profile of asubstrate that would result from subjecting the substrate a process;comparing the initial thermal profile to a desired thermal profile;adjusting a local amount of mass heated per unit area of a componentproximate the substrate in response to the comparison; and performingthe process to create the desired thermal profile on the substrate. 13.The method of claim 12, wherein adjusting the local amount of massheated per unit area comprises: varying the thickness of regions of asusceptor for supporting the substrate in response to the initialthermal profile.
 14. The method of claim 12, wherein adjusting the localamount of mass heated per unit area comprises: varying the thermalconductivity of regions of a susceptor for supporting the substrate inresponse to the initial thermal profile.
 15. A method of processing asubstrate, comprising: determining an initial thermal profile of asubstrate that would result from subjecting the substrate to a process;adjusting a local heat capacity per unit area of a component proximatethe substrate in response to a comparison of the initial thermal profileand a desired thermal profile; and performing the process to create thedesired thermal profile on the substrate.
 16. The method of claim 15,wherein adjusting the local heat capacity per unit area comprises:providing a multi-material susceptor for supporting the substrate,wherein the multi-material susceptor comprises regions of differentmaterials that compensate for the initial thermal profile to produce thedesired thermal profile.
 17. The method of claim 16, wherein thesusceptor comprises at least a first region and a second regionproximate the substrate, wherein the first and second regions havedifferent heat capacities.
 18. A method of processing a substrate,comprising: determining an initial thermal profile of a substrate thatwould result from subjecting the substrate to a process; comparing theinitial thermal profile to a desired thermal profile; adjusting anabsorptivity or a reflectivity of a component proximate the substrate inresponse to the comparison; and performing the process to create thedesired thermal profile on the substrate.
 19. The method of claim 18,wherein the component is at least one of an edge ring or an edge of asusceptor.
 20. The method of claim 18, wherein adjusting of theabsorptivity or reflectivity of the component comprises changing atleast one of a material composition, a surface property, or a thicknessof the component.